Knife sharpener



FIG. 1 is a front perspective view of a knife sharpener in accordance with the present design;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof;

FIG. 8 is a front perspective view of an alternate embodiment of a knife sharpener in accordance with the present design;

FIG. 9 is a left side elevational view thereof;

FIG. 10 is a right side elevational view thereof;

FIG. 11 is a front elevational view thereof;

FIG. 12 is a rear elevational view thereof;

FIG. 13 is a top plan view thereof; and,

FIG. 14 is a bottom plan view thereof.

The broken lines shown in the drawings illustrate portions of the knife sharpener that form no part of the claimed design. 

CLAIM The ornamental design for a knife sharpener, as shown and described. 